(a) Field of the Invention
The present invention relates to a concentrator type ATM switch for an ATM switching system and, more particularly, to a concentrator type ATM switch for use in an ATM switching system, which is capable of efficient transmission of information such as image, voice, and animation data.
(b) Description of the Related Art
An example of a typical ATM switching (network) system is shown in FIG. 1. This system includes a plurality of (m) comparatively small-scale nxc3x97n ATM switching modules 21 each including a nxc3x97n ATM switch 23, the ATM switching modules 21 being connected to one another through a coupling module 25 to form a large-scale ATM switching system. In this text, nxc3x97n switch as used herein means that the switch couples any one of n input ports to any one of n output ports, whereas n-to-1 selector and m-to-n multiplexer as used later mean that the selector selects any one of n inputs and the multiplexer multiplexes m signal sequences into n signal sequences.
In the ATM switching system of FIG. 1, a selector 22 is provided in each nxc3x97n ATM switch module 21 for selecting n cell data directly input therein or n cell data input through the coupling module 25 from another nxc3x97n ATM switch module 21. The n cell data selected by the selector 22 are supplied to the nxc3x97n ATM switch 23, which couples the same by switching to the output ports specified by the cell data.
The coupling module 25 receives mxc3x97n input data, or cell data supplied through mxc3x97n signal lines, which are supplied to the m ATM switch modules 21 and delivered from rout judgement blocks 24 in the ATM switch modules 21 after selecting the ATM switch modules 21 based on the destination of the data. A concentrator (or concentrator type ATM switch) 26 is provided in the coupling module 25 for each nxc3x97n ATM switch module 21. The concentrator 26 receives the mxc3x97n input data, supplied from one of the nxc3x97n ATM switch modules 21, to deliver the same to another of the nxc3x97n ATM switch modules 21 based on the destination of the data. That is, each concentrator 21 functions for multiplexing mxc3x97n signal sequences into n signal sequences.
The concentrator 26 may be of an output buffer type which stores all input data in output buffers after multiplexing the input data into a single signal sequence, of a knockout type which consecutively stores effective cell data in the output buffers from the first and discards the excess cell data if the number of effective cells to be processed at a time exceeds the number of the output ports, or of a switching type which functions for switching regardless of the order of the input cells and rearranges the order at the next stage of the switching.
The conventional concentrator 26 in the coupling module 25 as described above has a problem in that the transfer rate in the concentrator 26 rises along with the increase of the circuit scale that is increased by the number of ATM switch modules coupled by the coupling module 25. The increase in the transfer rate means that the upper limit of the physical performance of the concentrator 26 in the transfer rate restricts the scale of the ATM switching system obtained by the coupling.
Especially in the case of the knockout type concentrator, when the number of effective cells to be processed at a time exceeds the number of output ports provided therein, all the effective cells are not transmitted, resulting in a blocking switching operation of the system wherein excess effective cells are discarded.
It is therefore an object of the present invention to provide a concentrator type ATM switch, which is capable of suppressing the rise of the transfer rate therein and operating for a non-blocking switching wherein effective cells are not discarded.
It is another object of the present invention to provide an ATM switching system having the concentrator type ATM switch as described above.
The present invention provides, in one aspect thereof, a concentrator type ATM switch comprising a multiplexing block for receiving a plurality of (m) signal groups each including a plurality of (n) input signal sequences, the multiplexing block outputting n multiplexed signal sequences, a routing block for receiving the n multiplexed signals to output an assignment signal for each of effective input cells in the n multiplexed signals, and a concentration buffer block including an nxc3x97n banyan network having n input ports, n output ports and a set of switches for switching each of the effective cells supplied to the n input ports to one of the n output ports based on the assignment signal, and an output buffer block including n output buffers each for receiving effective cells through one of the output ports.
The present invention also provides, in another aspect thereof, an ATM switching system comprising:
a plurality of (m) ATM switch modules each having a plurality of (n) inputs each for receiving an input cell sequence, a routing judgement block for judging a destination of input cells in the input cell sequence to deliver a destination signal corresponding to each of the input cells, a selector for selecting n inputs from the inputs of own ATM switch module or the inputs of other ATM switch module, and a nxc3x97n ATM switch for receiving outputs from the selector; and
a coupling module having mxc3x97n input ports connected to the inputs of the m ATM switch modules, m output port groups each including n output ports, the output port group corresponding to the m ATM switch modules, at least one multiplexing block for multiplexing mxc3x97n signal sequences received from the plurality of ATM modules into n signal sequences, and m concentration buffer blocks each including a nxc3x97n banyan network and an output buffer block for receiving input cells in the n signal sequences from the multiplexing block to output the input cells through one of the output port groups to the selector of one of the ATM witch modules based on the assignment signal.
In accordance with the concentrator type ATM switch and the ATM switching system of the present invention, the rise in the transfer rate of the concentrator type ATM switch (concentrator) is suppressed, which enables a non-blocking switching operation wherein effective cells are not discarded.
The above and other objects, features and advantages of the present invention will be more apparent from the following description, referring to the accompanying drawings.